Synthesis gases are gas mixtures that are used in synthesis reactions and consist primarily of carbon monoxide and hydrogen. For some CO/H2 combinations, special names have established themselves, such as water gas, cracked gas, methanol synthesis gas or oxogas, because of their origin or use. Synthesis gas can be used as a starting mixture for the production of liquid fuels. Thus, synthesis gas is used, for example, in the Fischer-Tropsch process for generating diesel fuel. Gasoline fuels can be produced according to the MTG process (methanol to gasoline), in which synthesis gas is first converted to methanol, which is converted to gasoline in additional processing steps.
In principle, all substances containing carbon can be used for the production of synthesis gas. These include the fossil fuels—coal, crude oil and natural gas—as well as additional feedstocks such as, for example, plastic, peat, wood or other biomass such as municipal or agricultural waste. If solid matter is used, it must first be expensively reduced to small pieces, so that by partial oxidation or dissociation of steam, a raw synthesis gas can be generated. The raw synthesis gas is subsequently processed in additional steps. All of these steps lead to high investment costs, which are an obstacle for the production of fluid fuels from synthesis gas.
From EP 0 200 880 A2 it is known to mix converter gas with a high CO content from a blast furnace and coke-oven gas having a high hydrogen content and to use it as synthesis gas for methanol synthesis. In the known method, the coke-oven gas is first fed into a pressure swing adsorption system in which approximately 83% of the hydrogen contained in the coke-oven gas is separated. The residual hydrocarbon-containing gas is compressed, freed of catalyst poisons in a purification step, then converted and split in a steam reformer with the aid of water vapor into CO, CO2 and H2. The cracked gas is mixed with the previously separated hydrogen and mixed with enough converter to make a stoichiometric synthesis gas, and used as a methanol synthesis gas. Additional systems are required for the processing the coke-oven gas that was described, which are associated with corresponding investment and operating costs.